document.write( "Question 1137506: How do I find the formula for an exponential function that passes through the two given points?
\n" ); document.write( "(0,6) and (3,750)
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Algebra.Com's Answer #755382 by jim_thompson5910(35256)\"\" \"About 
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\n" ); document.write( "The general template for an exponential function is
\n" ); document.write( "\"y+=+a%2Ab%5Ex\"
\n" ); document.write( "where 'a' and 'b' are fixed values (constants).\r
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\n" ); document.write( "\n" ); document.write( "The first point given to us is (0,6) meaning that x = 0 and y = 6 pair up together. Let's plug them both into the template to see what happens
\n" ); document.write( "\"y+=+a%2Ab%5Ex\"\r
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\n" ); document.write( "\n" ); document.write( "\"6+=+a%2Ab%5E0\" replace x with 0; replace y with 6\r
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\n" ); document.write( "\n" ); document.write( "\"6+=+a%2A1\" anything to the zeroth power is equal to 1\r
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\n" ); document.write( "\n" ); document.write( "\"6+=+a\" one times any number is itself\r
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\n" ); document.write( "\n" ); document.write( "\"a+=+6\" So we have one of the constants we need.\r
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\n" ); document.write( "\n" ); document.write( "Now plug in the other point (x,y) = (3,750). Also we will plug in a = 6 that we found earlier. Then solve for b\r
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\n" ); document.write( "\n" ); document.write( "\"y+=+a%2Ab%5Ex\"\r
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\n" ); document.write( "\n" ); document.write( "\"y+=+6%2Ab%5Ex\" replace 'a' with 6\r
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\n" ); document.write( "\n" ); document.write( "\"750+=+6%2Ab%5E3\" plug in (x,y) = (3,750)\r
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\n" ); document.write( "\n" ); document.write( "\"750%2F6+=+%286%2Ab%5E3%29%2F6\" Divide both sides by 6\r
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\n" ); document.write( "\n" ); document.write( "\"125+=+b%5E3\"\r
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\n" ); document.write( "\n" ); document.write( "\"b%5E3+=+125\"\r
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\n" ); document.write( "\n" ); document.write( "\"root%283%2Cb%5E3%29+=+root%283%2C125%29\" Apply the cube root to both sides. You can also think of it as raising both sides to the 1/3 power. \r
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\n" ); document.write( "\n" ); document.write( "\"b+=+5\" We found the other constant\r
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\n" ); document.write( "\n" ); document.write( "Therefore,
\n" ); document.write( "a = 6
\n" ); document.write( "b = 5\r
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\n" ); document.write( "\n" ); document.write( "Making the function be \"f%28x%29+=+6%285%29%5Ex\" which is the same as \"y+=+6%285%29%5Ex\" since y = f(x).\r
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\n" ); document.write( "\n" ); document.write( "As a check, plug in x = 0 to get
\n" ); document.write( "\"f%28x%29+=+6%285%29%5Ex\"
\n" ); document.write( "\"f%280%29+=+6%285%29%5E0\"
\n" ); document.write( "\"f%280%29+=+6%281%29\"
\n" ); document.write( "\"f%280%29+=+6\"
\n" ); document.write( "So we get the proper output for the input x = 0. Repeat for the input x = 3 as well
\n" ); document.write( "\"f%28x%29+=+6%285%29%5Ex\"
\n" ); document.write( "\"f%283%29+=+6%285%29%5E3\"
\n" ); document.write( "\"f%283%29+=+6%28125%29\"
\n" ); document.write( "\"f%283%29+=+750\"
\n" ); document.write( "that output is correct as well. The function is confirmed. Both points are on the graph of this function curve.
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